Dishonored Wiki Guide

Devouring Swarm

Be careful! The rats will attack you if you are too close. Try to conjure the spell under an enemy's feet. Another useful note is that the rats can be possessed.

The group of rats can easily take down one opponent, but the odds of success decrease quickly as the number of enemies increases. Even if the rats are all killed, it still serves as a good diversion for your escape or so you can attack without fear of retaliation.